直流氩等离子体硅粉纯化工艺的研究

Technology parameters for Si particulates purity in DC Ar plasma

针对立式反应室、直流氩等离子体情况,建立硅粉的运动学模型,绘出粉粒沉降时间与粉粒粒度和进气速率的关系曲线,并通过该模型选择进气速率为4～10L/s,粉粒的粒度范围为70～100μm。为了提高粉粒沉降过程中纯化效果,建立并分析鞘层模型中与鞘层厚度、鞘层区离子浓度以及鞘层离子平均动能有关的工艺参数的变化关系并提出一套优化选择放电参数的方法。通过该方法优化工艺参数为反应室总压力为4～6Pa,阴极电压为2000V或是更高,鞘层厚度为1.2～2cm。提纯实验结果表明,硅粉的纯度可由99.6%提高到99.95%。

According to our chamber condition,the kinematic model was established for Silicon particulates,and figures of the relationship among the falling timediameter of Silicon particulates and the gas flow rates was protracted.The particulate diameters of 70-120μm,gas flow rates from 4-10L/s were chosen with the model and the figures.For the purpose of enhancing the effect of purity,the sheath model was established.The technology parameters related to the thickness,the ions density in the sheath area and the average kinetic energy of ions were analyzed on the basis of the sheath model.A method of choosing the technology parameters was provided.A sheath thickness of 1.2-2cm,the total chamber pressure from 4-6Pa and DC self-bias voltage of higher than 2000V were chosen using this method.The experimental results of etching purity showed the purity of Si powder can be increased from 99.6% to 99.95%.